1. Field of the Invention
The present invention relates to a measurement instrument, such as a radiation thermometer used in the measurement of a temperature of an object and, more particularly, to a protective shield that can conform to the surface of the object while protecting the object from the measurement instrument.
2. Description of Related Art
In the field of measurement instrumentation, there is sometimes a concern to protect an object to be measured from the measurement instrument. For example, in the field of radiation thermometers, it is frequently desired to use a radiation thermometer to measure the actual temperature of a highly polished metallic surface that can have a high gloss and will exhibit a low infrared emissivity. For example, the surface of a mold can be subject to a polishing treatment to ensure that an extremely smooth surface will be provided on the molded object. In the manufacturing of plastic lenses optical surfaces have to be carefully prepared. Thus, in plastic resin metal molds, glossy metal surfaces can be frequently found.
If a contact-type thermometer using a thermocouple came into contact with a glossy metal surface, it can mar or scratch such a surface to the detriment of the resulting molded product. Accordingly, a non-contact-type radiation thermometer is frequently recommended. The use of such a radiation thermometer can create another problem, however, in that a glossy metal surface can exhibit a low emissivity factor and can provide an erroneous reading. Attempts have been made to address this specific problem by attaching a black tape or black paint to the surface of the mold to provide a surface test area to enable an indirect measurement of the temperature of the object on the basis of a radiation dosage and an emissivity of infrared rays from the test area of the black tape or black paint when it is brought into a thermal equilibrium with the object to be measured.
As can be readily appreciated, however, the initial desire not to contact or mar the surface is compromised with a troublesome operation of sticking the tape onto the object or, alternatively, applying the black paint to prepare the test surface. Subsequent to the measurement operation, there is the additional problem of separating the tape or the paint from the test surface and, of course, there is always the possibility that the glossy metallic surface can be marred, injured or scratched when the tape or the paint is removed.
Thus, there is still a desire in the prior art to improve the method and apparatus of enabling a measurement of a temperature of a glossy metal surface with a high degree of accuracy.